Materials having a high dielectric constant may be used for forming a thin film in a semiconductor device such as a gate insulation layer of a metal oxide semiconductor (MOS) transistor, a dielectric layer of a capacitor or a dielectric layer of a flash memory device. The thin film including a high-dielectric (k) material may possess a thin equivalent oxide thickness (EOT) and may reduce the leakage current between a gate electrode and a channel, or between a lower electrode and an upper electrode. The thin film may also improve the coupling ratio of the flash memory device.
Examples of a high-k material include tantalum oxide (Ta2O5), yttrium oxide (Y2O3), hafnium oxide (HfO2), zirconium oxide (ZrO2), niobium oxide (Nb2O5), barium titanium oxide (BaTiO3), strontium titanium oxide (SrTiO3), etc.
A thin film including strontium titanium oxide (SrTiO3) may be formed using a strontium compound, a titanium compound as an organometallic compound and an oxidizing agent. A thin film including strontium ruthenium oxide (SrRuO3) may be formed using a strontium compound, a ruthenium compound as an organometallic compound and an oxidizing agent.
Examples of the strontium compound for forming the thin film including strontium titanium oxide or strontium ruthenium oxide may include strontium tetramethyl heptadione (Sr(TMHD)2) or strontium methylethoxy tetramethyl heptadione (Sr(METHD)2). Methylethoxy tetramethyl heptadione may serve as ligands for the organometallic compound.
A strontium oxide layer formed using Sr(TMHD)2 or Sr(METHD)2 may have a high dielectric constant. However, Sr(TMHD)2 or Sr(METHD)2 may be vaporized in a canister having a temperature of higher than about 250° C. In order to form the strontium oxide layer at a temperature of lower than about 250° C., considerable time may be involved to provide Sr(TMHD)2 or Sr(METHD)2 into a chamber. As the amount of time increases, throughput in the manufacturing process of semiconductor devices may decrease. Additionally, it may be beneficial to provide a method of forming a metal oxide layer having a high dielectric constant and a good step coverage using a material with suitable volatility.